From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [PATCH] tap: double-free in error path in tap_open() Date: Wed, 25 Oct 2017 09:55:40 +0800 Message-ID: References: <1508881270-4124-1-git-send-email-girish.moodalbail@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit To: Girish Moodalbail , netdev@vger.kernel.org, davem@davemloft.net Return-path: Received: from mx1.redhat.com ([209.132.183.28]:48307 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751323AbdJYBzo (ORCPT ); Tue, 24 Oct 2017 21:55:44 -0400 In-Reply-To: <1508881270-4124-1-git-send-email-girish.moodalbail@oracle.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 2017年10月25日 05:41, Girish Moodalbail wrote: > Double free of skb_array in tap module is causing kernel panic. When > tap_set_queue() fails we free skb_array right away by calling > skb_array_cleanup(). However, later on skb_array_cleanup() is called > again by tap_sock_destruct through sock_put(). This patch fixes that > issue. > > Fixes: 362899b8725b35e3 (macvtap: switch to use skb array) > Signed-off-by: Girish Moodalbail > --- > drivers/net/tap.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/drivers/net/tap.c b/drivers/net/tap.c > index 21b71ae..878520b 100644 > --- a/drivers/net/tap.c > +++ b/drivers/net/tap.c > @@ -542,20 +542,20 @@ static int tap_open(struct inode *inode, struct file *file) > > err = -ENOMEM; > if (skb_array_init(&q->skb_array, tap->dev->tx_queue_len, GFP_KERNEL)) > - goto err_array; > + goto err_put; Looks like this will cause skb_array_cleanup() to be called when skb array was uninitialized? Thanks > > err = tap_set_queue(tap, file, q); > - if (err) > - goto err_queue; > + if (err) { > + /* tap_sock_destruct() will take care of freeing skb_array */ > + goto err_put; > + } > > dev_put(tap->dev); > > rtnl_unlock(); > return err; > > -err_queue: > - skb_array_cleanup(&q->skb_array); > -err_array: > +err_put: > sock_put(&q->sk); > err: > if (tap)